Investigation of Foetal Auditory Abilities - Effects on Brain Activity

The research project will investigate foetal auditory abilities to perceive and process music in two separate study sets that either measure foetal heart rate (studies 1a & 1b, described separately) or foetal brain activity (studies 2a & 2b, present registration form). All studies will take place at Waikato Hospital and every participant will only take part in one of the study sets. Both study sets have two experiments which are separated by a five minute break in between to minimise carry over effects of foetal heart rate and brain activity responses between studies. One of the experiments investigates musical timbre perception by using audio files of three different instruments (clarinet, trumpet, violin) while the other experiment investigates foetal harmony perception using audio files of major and minor chords that are played by a piano. Studies 2a and 2b play the stimuli intermixed without silence blocks in between them. The presentation of the stimuli is controlled by a computer program written for the studies that ensures randomisation of all stimuli and counterbalancing across participants. The stimuli are delivered via a loudspeaker (Marshall Acton III Bluetooth Speaker) that is placed above the maternal abdomen. The total time of auditory stimulation will be 16.5 minutes for the brain activity studies including short periods of silence in between each individual stimulus in every experiment. Experimental conditions Study 2a - musical timbre timbres: clarinet, trumpet, violin (audio files) trials: nine trials per timbre with 3.492 sec sound (tone: C4 = 261.63 Hz) and 26.508 sec silence (30 sec per trial) sound pressure level: 95 dB Study 2b - chords chords: C-, G-, and D-major & a-, e-, and d-minor, all played by a piano (audio files) trials: four trials per individual chord (= 12 per category) with 1.327 sec sound (chord) and 28.673 sec silence (30 sec per trial) sound pressure level: 95 dB An individual study session will be between 54-67 min long and includes the following: One member of the research team will greet the mother-to-be and her whaanau or friends at the meeting point in front of the hospital and will bring her to the sonography unit where the studies will take place. They will then be taken through the participant information sheet and informed consent form. The participant information sheet includes an explanation of the purpose of the studies, explains the safety of the stimuli and methods used, has a brief description of the experimental procedure, and informs about what will be done to ensure the anonymity and the safety of the collected data. All explanations will be done in a clear, easy to understand language, and every participant will be asked for questions or concerns. Afterwards, the mothers-to-be will be asked to sign two copies of the informed consent sheet of which one of them will be given to the participant to keep for her records and one of them will be kept by the researchers. After written informed consent, the participant will be brought to the sonography room where every member of the research team present will be introduced and her or his role in the session will be explained. Next, the woman will lie down in a comfortable position on her back and routine foetal check-ups will be performed by a qualified and registered diagnostic medical sonographer with a current annual practicing certificate from the New Zealand Medical Radiation Technologists Board in Wellington. These check-ups will include measurements of the foetal bi-parietal diameter, head circumference, abdominal circumference, and femur length to estimate foetal weight and gestational age (GA). Furthermore, foetal heart rate (HR) as well as single deepest pocket of amniotic fluid will be recorded. The experimental procedure will then be explained in more detail and exemplary stimuli will be played to give the mothers-to-be an idea of what their babies will hear during the experiments. Each participant will be explicitly asked if she has any questions or concerns, and each will be reminded that the procedure can be stopped in case she feels uncomfortable or wants to withdraw. Neither of them must be justified. Then, the mother-to-be will be asked if she agrees to proceed with the procedure. If she does, she will be reminded to remain silent during the experiments and to lie as still as possible to ensure a high quality of the collected data throughout the experimental parts. Next, the research team will identify foetal position as well as foetal behavioural state (after Nijhuis et al., 1982) using 2D-ultrasound. To access fronto-temporal brain activity in studies 2a and 2b a particular position of the foetus will be required. The near-infrared light of fNIRS penetrates up to 5 cm into the maternal abdomen (Araki & Nashimoto, 1992) and if the foetal head is not within this range, the participant will be asked to be taken for a short walk or to drink a glass of water to stimulate foetal repositioning. Otherwise, the experimental procedure cannot be continued, and the women will be asked to return a few days later if she is still interested in participating. If the foetus is in an appropriate position, the fNIRS probe and the loudspeaker will be put into place, headphones will be given to the mother-to-be and her company and the experiments will start. After the completion of both experiments, the mothers-to-be will be asked if they have heard any of the stimuli or if they felt any foetal movement during the session. Everyone will be thanked for participating, debriefed, and given the opportunity to ask further questions or to comment about the studies. Every participant will be given $ 30 vouchers in recognition of travel costs and to show appreciation of taking part in the studies as well as a debrief form that summarises the studies in easy to understand language. The debrief form also includes the contact details of the primary investigators and two recommendations for further reading if the mothers-to-be have any further interest in pregnancy, foetal, and early development in general. References Araki, R., & Nashimoto, I. (1992). Near-infrared imaging in vivo (II): 2-dimensional visualization of tissue oxygenation state. In T. K. Goldstick, M. McCabe & D. J. Maguire (Eds.), Oxygen Transport to Tissue XIII (pp. 173-178). Springer. https://doi.org/10.1007/978-1-4615-3404-4_20 Nijhuis, J. G., Prechtl, H. F. R., Martin, C. B., & Bots, R. S. G. M. (1982). Are there behavioural states in the human fetus?. Early Human Development, 6(2), 177-195. https://doi.org/10.1016/0378-3782(82)90106-2